With the draft just two days away, a roadblock has arisen in negotiations with the Chinese Basketball Association that could prevent 7-5 center Yao Ming from being drafted Wednesday, sources in China told The Post late last night.

Because of Maverick forward Wang Zhi Zhi’s decision not to return to China this month for national-team practices and fearing his defection, the Chinese Basketball Association now wants a written document from the NBA, guaranteeing Ming’s participation in all Chinese National Team functions.

Ming’s agent, Erick Zhang, who is based in Chicago, has been in China negotiating with Chinese basketball officials the past few days.

If there’s no agreement with the Chinese Basketball Association, Ming may not get clearance from FIBA, the international governing body, and then is not eligible to be drafted.

Ming will be the top pick in the draft by Houston if the FIBA clears him. If not, the Rockets could wind up trading the pick because it does not want point guard Jay Williams. The Knicks have maintained constant dialogue with Rockets GM Carroll Dawson.

Lou Hong Liang, an interpreter for the Shanghai Sharks, told The Post last night, “The CBA is afraid. The only concern is whenever the national team meets, he can come back and no one can guarantee this.”

The Sharks’ official added, “I think it’s difficult. Will the NBA write a guarantee for that? If they will, that’s OK. If the NBA writes the guarantee, everything will be OK but there seems to be no agreement. If he can’t go, he’ll play for the Sharks and the national team.”

The Rockets aren’t involved in the negotiations. A source familiar with the situation told The Post that Chinese officials don’t trust Ming’s representative, Zhang, because he may have had contact with Zhi Zhi, who’s reportedly in northern California. The concern is Ming could be a threat to defect, too. Ming won’t attend the draft because of national team practices.

A Rocket spokesman said last night, “Our position is we’re waiting on the sidelines. As far as we’re concerned, there’s not a role for us to play.”

An NBA spokesman had no knowledge of the CBA’s new demands.

Chinese officials also believe Zhang “exaggerated” in his press conference Saturday in China in which he announced an agreement with the Sharks regarding compensation, indicating they had cleared their most important hurdle. Lou Hong Liang pointed out that no Shanghai Shark official was present at the news conference.

Two days ago, Zhang said, “The CBA will give us a reply to our proposal by Monday so I hope an agreement can be reached with the CBA quickly and I’m confident it can be reached before the draft.”